Immunofluorescence techniques were developed and optimized, using multiple fluorochrome-labeled antibodies, to achieve simultaneous identification of two or three types of inflammatory cells in the hearts of rats with myocarditis caused by treatment with interleukin-2. Cells identified by these techniques included natural killer cells, lymphokine-activated killer cells, T-helper cells, T-suppressor cells, macrophages and 3 subpopulations of interstitial dendritic cells.